WO2003101579A1

WO2003101579A1 - Method for removing water contained in solid using liquid material

Info

Publication number: WO2003101579A1
Application number: PCT/JP2003/006989
Authority: WO
Inventors: Hideki Kanda; Hiromi Shirai
Original assignee: Central Research Institute Of Electric Power Industry
Priority date: 2002-06-03
Filing date: 2003-06-03
Publication date: 2003-12-11
Also published as: CA2487641A1; EP1524019A1; AU2008250084A1; CN1658937A; EP1524019B1; EP1524019A4; US20050210701A1; JPWO2003101579A1; CN100350996C; US7537700B2; CA2487641C; AU2003241902A1; AU2003241902B2; JP4291772B2

Abstract

A method for removing the water contained in a solid, which comprises contacting a solid containing water with a liquefied material which is a gas at 25°C under 1 atm. (hereinafter referred to as the material D) to allow the liquefied material D to dissolve the water contained in the solid, to produce a liquefied material D having a high water content and simultaneously remove the water from the solid, vaporizing the material D in the liquefied material D having a high water content, to thereby separate water from a gaseous material D, recovering the gaseous material D, and liquefying the gaseous material D by pressuring, cooling, or a combination thereof, for reuse; and a system for practicing the method. The method can be suitably employed for removing water from a solid having a high water content such as a high water content coal with a reduced energy consumption.

Description

Specification

Method for removing solid-containing water using liquefied substance

Technical field

The present invention relates to dehydration from water-containing solids, and more particularly, to a method and a system for dewatering water-containing solids at an operating temperature close to the outside air temperature and with a small required power. .

Background art

Conventionally, there has been a method of removing water from a water-containing solid by evaporating the contained water, but in recent years, without using the latent heat of evaporation of water, water has not been evaporated. A solvent replacement method of dehydrating while keeping the form in a liquid state has also been attempted.

As a method for evaporating and removing water, for example, there is a dehydration method using a dry inert gas as disclosed in JP-A-10-338653. In this method, the difference between the saturated vapor pressure of water and the water vapor pressure in the dry inert gas is the driving force for dehydration. The theoretical maximum amount of water that can evaporate into the dry inert gas is estimated to be proportional to the saturated vapor pressure of water, the density of water vapor, and the volume of the dry inert gas. Since the vapor pressure is significantly lower than 101325 Pa, and the density of water vapor is extremely small as compared with liquid water, the inert gas dehydrator described in this publication necessarily has a large capacity. Dehydration treatment with an inert gas is required. The apparent capacity can be reduced by increasing the number of circulations, but the total gas throughput is not significantly reduced. This problem applies not only to the case where the dehydration target is a liquid as shown in this publication but also to the case where the dehydration target is a solid.

In order to solve the problem that the saturated vapor pressure of water near room temperature is significantly lower than 101325 Pa, if the object to be dehydrated is a substance that can be heated to 100 ° C or more, dry Heating to more than ° C and increasing the saturated vapor pressure of water vapor to more than 101325 Pa reduces the amount of gas (hot air drying method). However, the method of evaporating moisture in solids by the hot air drying method requires a heat source to heat the inert gas to 100 ° C or more and a heat source to evaporate the moisture. To perform dehydration, the latent heat of vaporization of the water vapor evaporated in the inert gas is used. It is important to collect efficiently. However, in the hot-air drying method, the vapor evaporating from the solid is diluted into the inert gas, so that the density of the latent heat of vapor contained in the vapor is significantly reduced (entropy is increased). However, there is a problem that the decrease in temperature cannot be avoided thermodynamically.

On the other hand, in the in-oil reforming method (JP-A-2000-290673), coal is assumed as the water-containing solid, and the water-containing solid slurried in oil is heated at 150 ° C or more to reduce the water content. The water content of the contained solid is evaporated. Since only water is selectively evaporated by using liquid oil, which hardly evaporates at the operating temperature, as the heating medium, the steam is not diluted, and the density of the latent heat of evaporation of the steam does not decrease. For this reason, the latent heat of vaporization of the steam can be efficiently recovered by the in-oil reforming method. In particular, regarding the dewatering of coal, it is considered that the energy required for the in-oil reforming method is the smallest among the existing methods. [The Institute of Energy Engineering, New Energy Outlook Low-grade coal reforming technology (1997)]. However, in the oil-in-oil reforming method, centrifugation and heating operations are required to separate the dewatered solid from the slurry oil, so some kind of energy input is required. Note that the energy required for the entire process is

2100 kJ / kg water (Institute for Advanced Energy Engineering, prospects for new energies Low-rank coal reforming technology (1997), p268, heat and mass balances calculated from Tables 5 and 29).

On the other hand, solvent replacement, which assumes coal as a water-containing solid and does not use the latent heat of evaporation of water, does not evaporate the water of the water-containing solid and dehydrates the water while keeping the water in liquid form. Method [K. Miura, K. Mae, R. Ashida, T. Tamaura and T. Ihara, The 7th Cnina-Japan Symposium on Coal and CI Chemistry Proceedings p351 (2001)). In this solvent displacement method, there are two cases using a non-polar solvent and a polar solvent.

Since polar solvents have high water solubility even at normal temperature and normal pressure, it is possible to dissolve the water in the water-containing solid without raising the temperature, but a distillation operation is required to separate the completely mixed polar solvent and water. . A great deal of heat energy is consumed in this distillation operation. This can be regarded as dehydration energy replaced by distillation energy, and is not a drastic measure to reduce dehydration energy. On the other hand, non-polar solvents hardly dissolve water at room temperature, but when heated under high pressure while maintaining the liquid state without evaporating the non-polar solvent, a small amount of water is dissolved. Applying this property, after dissolving the moisture of the water-containing solid in a high-temperature, high-pressure nonpolar solvent, the nonpolar solvent is cooled to room temperature to separate water that cannot be dissolved in the nonpolar solvent. In this way, dehydration without evaporating water may reduce the required energy even more than before, but the operation of separating the water-containing solid from the liquid organic solvent must be performed. We need energy for this.

The process also requires heating of the solvent and recovery of the heat released during cooling. As long as the heating pipe and the cooling pipe of the solvent are connected by a heat exchanger, even if the solvent is ideally heated without considering heat loss, the temperature rise on the heating side corresponding to the approach temperature of the heat exchanger. It is essential. This heating energy is the product of the amount of solvent, the heat exchange approach temperature, and the heat capacity at constant pressure of the solvent. Here, the approach temperature is the temperature difference between the two tubes to transfer heat from the cooling tubes (high-temperature medium) to the heating tubes (low-temperature medium) in the heat exchanger.

The inventors estimated the required energy when using tetralin, which was assumed as the nonpolar solvent in the above literature, to be 2284 kJ / kg—water. In this estimation, a small value at 25 ° C was used for the solvent's molar heat capacity at constant pressure instead of the value at the actual operating temperature of 145-150 ° C, and heat loss was not considered. Energy is bigger than this. The method using this tetralin exceeded the required energy of the whole process of the in-oil reforming process of 2100 kJ / kg—water by heat exchange alone. In addition to heat exchange, energy is also required to circulate the solvent in the process, and this non-polar solvent method cannot reduce the energy required for water removal.

As described in the above-mentioned conventional technology, even in the oil reforming method requiring the minimum energy, heating must be performed to evaporate water from the water-containing solid, and the heating at a high temperature exceeding 100 ° C is required. A dehydration operation is required, and there is a problem that the equipment cost and the running cost of the equipment are large.

The present invention provides dewatering under temperature conditions close to the outside air temperature, that is, approximately 0 ° (: up to 50 ° C), and efficiently recovers chemical substances used for dehydration. A dewatering method that requires less energy and requires less energy, and that is suitable for performing the method of the present invention, and that is excellent in heat exchange and work recovery. To provide.

Disclosure of the invention

According to the present invention, a liquefied substance of a substance which is a gas at 25 ° C. and 1 atm (hereinafter referred to as “substance D”) is brought into contact with the moisture-containing solid to dissolve the solid-containing moisture in the liquefied substance of the substance D. To remove the solid water by converting it into a liquefied substance of high water content D, and separating the gas and water of substance D by vaporizing substance D in the liquefied substance of high water content D Then, the separated gas of substance D is recovered, and the recovered gas is liquefied by pressurization, cooling, or a combination of pressurization and cooling, and used again for removing the water of the water-containing solid. It is intended to provide a method for removing solid-containing moisture using a liquefied substance.

Further, the present invention provides a substance which is a gas at 25 ° C. and 1 atm (hereinafter referred to as a substance D), a compressor for pressurizing the gas of the substance D, and a gas for the pressurized substance D. A condenser that condenses to a liquefied substance; a dehydrator that contacts the liquefied substance of substance D with a water-containing solid to dissolve and dehydrate water; and a substance that vaporizes substance D from a liquefied substance of dissolved substance D Evaporator, a separator for separating the vaporized substance D and water, and an expander for expanding the vaporized substance D are connected in series, and this expander is connected to the compressor to form a circuit. The substance D is circulated through this circuit, the condenser and the evaporator are connected by a heat exchanger, and the work performed to the outside in the expander is recovered. This work is one of the power of the compressor. Characterized in that it is configured to be charged as a part The present invention provides a water removal system. Here, from the separator, a degassing tower for degassing the substance D from the water separated by the separator is connected, and the degassing tower is connected to the circuit described above, and the degassed substance D is Preferably, it is configured to be recovered and returned to the circuit.

Here, the substance which is a gas at 25 ° C. and 1 atm is preferably one or a mixture of two or more selected from dimethyl ether, ethyl methyl ether, formaldehyde, ketene, and acetoaldehyde. The contact between the liquefied substance of the substance D and the water-containing solid is not particularly limited, but it is preferable to make the countercurrent contact. More preferably, the amount of the liquefied substance of the substance D that comes into contact with the water-containing solid is not particularly limited, but is preferably a stoichiometric amount in order to suppress the extraction of components other than water from the solid. The water removal method of the present invention is suitable for removing solids containing a large amount of moisture at an operating temperature close to the outside air temperature and with a small amount of required power, and is applicable to all types of moisture-containing solids. The moisture-containing solid is preferably lignite or subbituminous coal, which enables to achieve the combustion performance and transportation cost equivalent to high-grade coal. Further, the lignite or subbituminous coal dewatered according to the present invention is suppressed from rewetting, so that it is not necessary to take measures such as adding heavy oil to suppress rewetting.

According to the present invention, as the dehydrating medium, a liquefied substance of a substance having a high mutual solubility with water, which is a gas at atmospheric pressure and at a temperature close to the outside temperature is used, so that the liquefied substance is evaporated after dehydration. As a result, it can be easily separated from moisture, and dehydration can be performed at an operating temperature close to the outside air temperature as compared with the conventional technology. In addition, there is no need to evaporate the water for the separation of the water, and there is no need to collect the latent heat of evaporation of the water. In addition, the liquefied gas can be efficiently recovered and circulated for use.In the system, latent heat of vaporization can be recovered and effectively used by the heat exchanger, and work due to expansion can be recovered efficiently. And further energy savings can be achieved. That is, according to this system, after the water content of coal is dissolved in liquefied dimethyl ether, the temperature and pressure are slightly changed to selectively evaporate only dimethyl ether from the liquid mixture of liquefied dimethyl ether and water, Water and dimethyl ether can be easily separated, and the water can be removed from the coal without evaporating, and the evaporated dimethyl ether can be liquefied and recycled.

Furthermore, by degassing the separated wastewater, liquefied matter was easily removed and the burden on the environment was reduced.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram of an example of the system of the present invention. FIG. 2 is a schematic diagram showing temperature and pressure conditions of an example of the system of the present invention. Figure 3 is a graph showing the power required for the second compressor with respect to the heat insulation efficiency of the expander and the heat insulation efficiency of the compressor. Figure 4 shows the results of the dehydration experiment. Figure 5 is a graph showing the relationship between the water content of Roy Young coal and the relative humidity. Figure 6 shows the amount of liquefied dimethyl ether that was circulated, the amount of water removed, and the amount of precipitated dimethyl ether. It is a graph which shows the relationship with the combustible content of lignite.

BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, in order to remove water, a liquid that is a gas that is liquefied at 25 ° C. and 1 atm is used as a liquid to be brought into contact with a solid containing water.

The solvent replacement method using a non-polar solvent, which is one of the conventional water removal methods, uses the property that the solubility of water is increased by raising the temperature of the solvent. It is characterized by the fact that the solubility of water is significantly changed by utilizing the gas-liquid phase transition phenomenon of the solvent in order to save energy in the law. That is, a substance in a gaseous state at room temperature is pressurized or cooled to a liquid state, and this is used as a replacement solvent. If the temperature and pressure are changed slightly after dissolving the water in the solid in the liquefied solvent, only the solvent is selectively evaporated and the water and solvent gases are easily separated.

Therefore, as the solvent used in the present invention, a substance having high mutual solubility with water and having high mutual solubility with water in a liquefied state is desirable.

Further, if the boiling point of the solvent is higher than room temperature, a high-temperature energy source is required to evaporate the solvent when separating from water, and it is expected that the energy required for dehydration will increase. In order to enable dehydration with a small amount of required energy, the boiling point of the solvent is preferably around room temperature or lower. Therefore, in the present invention, a substance that is a gas at 25 ° C. and 1 atm is liquefied and used. Even more preferred are substances that are gaseous at 0 ° C. and 1 atm. Substances that are gaseous at 25 ° C and 1 atmosphere include dimethyl ether, ethynolemethyl ether, formaldehyde, ketene, and acetoaldehyde. These may be used alone or as a mixture of two or more. Among them, dimethyl ether and dimethyl ether which are easy to handle without toxicity are preferable. Butane and propane are also substances that are gaseous at 25 ° C and 1 atm. These do not have the ability to dissolve water by themselves, but can be mixed with one or more mixtures selected from dimethyl / ether, ethyl methyl ether, formaldehyde, ketene, acetoaldehyde, etc. it can. Since butane and propane are components of natural gas and the like, they are easily available and can be easily liquefied because they have a boiling point close to that of liquefied dimethyl ether. Moreover, even if it is used by mixing with liquefied methyl ether, etc., the dehydration performance is slightly reduced. Since it is possible to obtain sufficiently superior performance compared to the method, it is possible to reduce the use of liquefied dimethyl ether and the like.

In the method of the present invention, a liquefied substance of such a substance is brought into contact with a water-containing solid, and water in the solid, that is, pores on the outer surface of the solid, between the solid particles, and in some cases, inside the solid particles The water in the water-containing solid is dissolved in the liquefied material by contact with the water present in the water, and the water-containing solid is dehydrated. The contacting method may be any method used in a normal dehydration method, such as immersion or flowing a liquefied substance to a solid.

The liquefied material having a high moisture content can be easily separated from the liquefied material by vaporizing only the liquefied material. Evaporation can be performed by increasing the temperature or the pressure. The liquefied material used in the present invention is a gaseous substance at a temperature close to the outside air temperature, so depending on the pressure at the time of the vaporization operation, it does not require much heating to vaporize and can be vaporized at around normal temperature. . The vaporization temperature is preferably 0 ° C. to 50 ° C., although it depends on the liquefied material used. The pressure of the liquefied material during vaporization is naturally determined by this temperature. The vaporized liquefied matter is collected, liquefied, and brought into contact with a solid containing water again to be used for water removal. The liquefaction is performed by pressurization, cooling, or a combination of pressurization and cooling, and advantageous conditions are appropriately selected in consideration of the boiling point of the substance to be used. If the substance has a boiling point of 0 ° C or less at 1 atm, if liquefaction is performed by cooling only without applying pressure, the temperature of the liquefied substance will be 0 ° C or less and dehydration will not be possible. It is necessary to liquefy at a higher temperature, and liquefaction is performed by a combination of pressurization and cooling. In addition, in the case of a substance having a boiling point of more than 0 ° C. at 1 atm, liquefaction is preferably performed at a temperature equal to or higher than the boiling point. This is because below the normal boiling point, the saturated vapor pressure of substance D is less than 1 atmosphere, which causes the internal pressure of the equipment to be less than 1 atmosphere, which increases the manufacturing cost of the equipment and makes handling difficult. is there. The temperature of the liquefied material is preferably between 0 ° C. and 50 ° C., from which the pressure is determined. From the above, in the method of the present invention, by changing the pressure and temperature, a series of dehydration operations can be performed in a temperature range of about 0 ° C. to 50 ° C. Can be.

The method of the present invention can be applied to moisture removal of any solid including coal.

In the water removal method of the present invention, a liquid is used as a medium for dehydration, The difference between the saturated solubility of water and the concentration of water in the liquefied product is the driving force for dehydration. The theoretical maximum amount of water that can be dissolved in the liquefied product is proportional to the saturated solubility of water, the density of water, and the volume of the liquefied product. Comparing this with the theoretical maximum value of the amount of water that can evaporate in a dry inert gas as described in the section of the prior art, the saturated solubility of water is approximately 6% around 20 ° C. Very high relative to the saturated vapor pressure partial pressure of water vapor in the air (approximately 2%). Such extremely high mixing ratios are not possible with gases, and here is the feature of using liquids as a medium for dehydration. Also, since the density of water is much higher than the density of water vapor, dehydration with a small amount of liquefied material is possible.

Also, when dehydrating with a dry inert gas, the water vapor mixed in this gas is diluted, so that the density of latent heat of vaporization is reduced, making it difficult to recover latent heat of vaporization. In the practical application of the process for dehydrating a large amount of substances, effective recovery of latent heat of vaporization is important, and the dehydration method using gas as a medium is limited to small-scale processes.

However, when a liquid is used as a dehydrating medium as in the present invention, water can be removed without evaporating, and the recovery of the latent heat of evaporation itself becomes completely unnecessary. In addition, since it is a gaseous substance at around ambient temperature and under normal pressure, it is easy to separate liquefied matter and moisture, and dehydration with energy saving is possible.

A dehydration system suitable for practicing the water removal method of the present invention is shown below. FIG. 1 is a schematic diagram showing the configuration of an example of the water removal system of the present invention.

In this example, it is assumed that dimethyl ether is used as the substance D which is a gas at 25 ° C and 1 atm, and that coal is dehydrated as a water-containing solid, but the system of the present invention is not limited to this. Not something. Dimethyl ether has a boiling point of about −25 ° C. at 1 atm and is in a gaseous state at an atmospheric pressure of 0 ° C. to 50 ° C. As described above, since it is in a gaseous state at around room temperature and under atmospheric pressure, it is necessary to operate under pressure to obtain dimethyl ether in a liquid state. Also, a highly efficient method and apparatus for producing dimethyl ether are described in, for example, JP-A-11-303074, JP-A-10-195009, JP-A-10-195008, JP-A-10-182535 to JP-A-10-182527. JP-A-09-309852 to JP-A-09-309850, JP-A-09-286754, These are disclosed in JP-A-09-173863, JP-A-09-173848, JP-A-09-173845, etc., and can be easily obtained.

Compressor 1, 1 'for pressurizing dimethyl ether vapor, Condenser 2 for liquefying pressurized vapor, Contacting liquefied dimethyl ether with water in solid containing water to dissolve water A dehydrator 3 for dehydrating and an evaporator 4 for evaporating dimethyl ether from liquefied dimethyl ether containing water by dehydration are connected in this order.The condenser 2 and the evaporator 4 are connected by a heat exchanger 5. I have. Next to the evaporator 4, a separator 6 for dimethyl ether vapor and water, and an expander 7 for adiabatically expanding the dimethyl ether vapor separated by the separator 6 are connected in series by piping, and the expander 7 is further connected to a compressor. 1 and form a closed circuit (circulation path). In this circuit, dimethyl ether circulates while changing the state of gas and liquid, repeating dehydration and separation of water. In addition, 4 'in Fig. 1 is a cooler and 4 "is a pressure reducing valve, which adjusts the temperature and pressure when vaporizing liquefied dimethyl ether and is considered to be part of the evaporator. The separator 6 is connected to a degassing tower 8 for degassing the dimethyl ether dissolved in the water separated by the separator 6. In the degassing tower 8, the pressure inside the degassing tower is controlled by a pressure-holding valve 8 '. The degassing tower 8 is connected to the circuit described above, and the recovered dimethyl ether is returned to the circuit again by a piping (not shown).

In the expander 7, the work performed in the outside world is collected here, and this work is used as a part of the power of the compressor 1 that pressurizes the dimethyl ether. In the system of Fig. 1, the compressor has two stages, the first compressor 1 and the expander 7 are connected, and the work performed by the expander 7 is collected and used as the power for the first compressor 1. . Reference numeral 9 denotes an electric motor, and external work is input only to the second compressor 1 '. The work performed to the outside world in the expander 7 includes a force S mainly indicating a work performed by the dimethyl ether gas in accordance with the volume expansion, and also includes a work described below. The superheated gas of dimethyl ether that has exited the evaporator 4 may be mixed with droplets that are entrapped in the flow of the superheated gas. For this reason, in the expander 7, work may be obtained by vaporization of the mixed droplets. In the present invention, the work performed by the expander 7 includes not only the work due to the volume expansion of the superheated gas but also the work. Further, since the condenser 2 and the evaporator 4 are connected by the heat exchanger 5, the latent heat of vaporization of the liquefied dimethyl ether is recovered and used effectively.

In addition, a cooler 10 may be installed in the system of the present invention as shown in FIG. This is installed as necessary depending on the conditions of the liquefied gas to be used and the like, and adjusts the temperature of the gas discharged from the expander 7 to the optimum temperature at the inlet of the compressor 1. This system involves three types of water-containing solids: coal, water, and liquefied dimethyl ether. Focusing on each substance, the flow of this system is described.

The water-containing solid coal is charged into the dehydrator 3 and is removed from the container after being dehydrated by liquefied dimethyl ether. In FIG. 1, the flow is indicated by a dotted line.

The water whose flow is indicated by a double line in FIG. 1 is supplied from the dehydrator 3 to the system as moisture of the moisture-containing solid. First, it is eluted into liquefied dimethyl ether by the dehydrator 3 and then reaches the evaporator 4 in a form dissolved in the liquefied dimethyl ether. Most of the liquefied dimethyl ether is vaporized in the evaporator 4, and the water dissolved in the liquefied dimethyl ether is separated. It is separated into dimethyl ether vapor and water by the gas-liquid separator 6, and the water remains as wastewater. Since the pressure inside the gas-liquid separator 6 is higher than the atmospheric pressure, dimethyl ether gas is dissolved in the aqueous phase separated by the gas-liquid separator 6. If this water is discharged as it is, the burden on the environment will be great, and the loss of dimethyl ether will increase. Therefore, in order to minimize the burden on the environment and the loss of dimethyl ether, it is necessary to install a de-dimethyl ether column to recover dimethyl ether. In the case of the present embodiment, a degassing tower 8 is used as the dedimethylether tower. Is configured. Further, by heating the water with a heating can 8a provided at the lower part of the degassing tower 8, the recovery of dimethyl ether can be improved. The degassed water is discharged as bottoms, and the dimethyl ether vapor separated from the wastewater can be returned to the circuit of the dehydration system and used again.

The dimethyl ether gas whose flow is shown by a solid line in FIG. 1 is pressurized by the compressors 1 and 1 ′ to become a superheated gas, and then becomes a supercooled liquid in the condenser 2. Liquefied dimethi The supercooled liquid of the luter is supplied to the dehydrator 3 to dissolve the water of the water-containing solid, and flows to the evaporator 4. The liquefied dimethyl ether is separated from water in the evaporator 4 and becomes a superheated gas again. At this time, since the condenser 2 and the evaporator 4 are connected by the heat exchanger 5, the latent heat of vaporization of the liquefied dimethyl ether is recovered and effectively used. The superheated gas of dimethyl ether leaving the evaporator 4 works in the expander 7 and is recovered as a part of the compressor power. The dimethyl ether gas exiting the expander 7 is sent again to the compressor 1 and circulates through the system.

FIG. 2 shows an example of setting the phase state, pressure, temperature, and saturation temperature when dimethyl ether is used in one example of the system of the present invention. To simplify the design of pressure and temperature, the degassing tower 8 for dimethyl ether gas from water was omitted, and it was assumed that water and dimethyl ether could be completely separated by the gas-liquid separator 6. It was also assumed that the water-containing solid treated in the dehydrator 3 did not contain dimethyl ether.

First, the temperature and pressure conditions were set with the temperature at the inlet of the first compressor 1 as a starting point. When the temperature at the inlet 第 of the first compressor is 25 ° C and it is overheated by 10 ° C from the saturation temperature (b.p.l 5 ° C), the pressure becomes 0.44 MPa. As the degree of superheat is smaller, the pressure in the first compressor 1 increases, and the power of the compressor 1 decreases.On the other hand, dimethyl ether gas is cooled by outside air and condensed at the stage just before the compressor inlet. The danger increases. In addition, since the heat capacity ratio of dimethyl ether is as small as 1.11, the temperature does not easily rise during adiabatic compression. For this reason, the degree of superheat at the compressor outlets 1 and 3 at the first compressor 1 and the second compressor 1 'is smaller than the superheat at the compressor inlet. In this system, when determining the superheat at the compressor inlet, it is necessary to pay attention to the superheat at the compressor outlet.

The pressure at the outlet ③ of the second compressor 1 ′ is determined by the temperature of the cooling water used for the cooler 4 ′ before the evaporator 4. Here, it is assumed that the outside air temperature is 20 ° C and the temperature of the cooling water is equal to the outside air temperature. Assuming that the approach temperature at cooler 4 'is 5 ° C, the temperature of liquefied dimethyl ether at the outlet (evaporator inlet) ⑥ of cooler 4 is 25 ° C. Further, if the approach temperature between the condenser 2 and the evaporator 4 is 5 ° C, the temperature at the outlet の of the condenser 2 is 30 ° C. Subcooling at 5 ° C at the outlet of condenser 2 (inlet of dehydrator 3 and in dehydrator 3) so that dimethyl ether in dehydrator 3 can be stably present as a liquid When the pressure is set, the operating pressure of the condenser 2 (pressure at the compressor outlet) is determined. In this case, since the saturation temperature is 35 ° C, the outlet (2) of the condenser 2 and the outlet (condenser inlet) (3) of the compressor 1 'are 0.78 MPa. Also, assuming adiabatic compression, the temperature at the outlet ③ of the second compressor 1 'was 43 ° C, confirming that the temperature exceeds the saturation temperature of dimethyl ether at the compressor outlet.

Since the saturation temperature of the evaporator 4 is 30 ° C, it is necessary to reduce the pressure at the inlet における of the evaporator 4 to the saturation pressure at 30 ° C. The saturation pressure here is the saturation pressure of a mixture of water and liquefied dimethyl ether, and is 0.62 MPa. Since the temperature difference ΔΤ between the condenser 2 and the evaporator 4 is 5 ° C, the temperature at the outlet (expander inlet) 入口 of the evaporator 4 is 38 ° C. Since the degree of superheat here is 8 ° C, the heat loss within the energy required to heat the dimethyl ether gas at 8 ° C is reduced from the outlet of the second compressor 1 ′ to the inlet of the expander 7. Is acceptable.

After separating dimethyl ether gas from water by the gas-liquid separator 6, the expander 7 adiabatically expands the water. The pressure at the outlet の of the expander 7 is equal to the pressure at the inlet of the first compressor 1. The dimethyl ether gas is cooled to 26 ° C by adiabatic expansion. Cooling is necessary because the temperature is 1 ° C higher than the inlet of the first compressor 1. In the expander 7, energy is recovered and used as power for the first compressor. Assuming that the adiabatic efficiency of the expander 7 and the first compressor 1 is 80%, the temperature at the outlet of the first compressor is 32 ° C and the pressure is 0.55 MPa.

Furthermore, the required power in the second compressor 1 'is calculated by variously changing the adiabatic efficiency in the expander 7 and the two compressors 1 and 1' in accordance with the temperature and pressure settings already determined.

First, the total work required by the two compressors 1, 1 'is (theoretical work required by the two compressors 1, 1') ÷ (adiabatic efficiency). On the other hand, the work collected by the expander 7 and input as power for the first compressor 1 is (theoretical work performed by the expansion) X (adiabatic efficiency). Therefore, the work required for the second compressor 1 'is (theoretical work required for the two compressors 1, 1') ÷ (adiabatic efficiency) Theoretical work performed by one expansion) X (adiabatic efficiency). Furthermore, since this work needs to be introduced in the form of power, assuming that the conversion efficiency is 0.35, the work required by the second compressor 1 ') ÷ 0.35 requires the second compressor 1' Total energy. This conversion rate is the same value as the conversion efficiency of the compression power for latent heat recovery of steam, which was used in the power estimation of the in-oil reforming method.

Here, assuming that dimethyl ether is an ideal gas and adiabatic compression is assumed, the power required for the second compressor 1 ′ as shown in Fig. 3 is obtained for the adiabatic efficiency of the expander 7 and the adiabatic efficiency of the compressor 1. Can be

If the insulation efficiency of both compressor 1 and expander 7 is 0.8, the required power of this system will be 948kJ / kg water. The compression efficiency is based on the compression efficiency of the compressor used for estimating the latent heat of steam used in the power estimation of the in-oil reforming method. Technology (1997)].

As shown in the estimation results, it was theoretically confirmed that it was possible to achieve a small dehydration of required energy, which is a problem to be solved by the invention.

(Example 1)

Further, the following experiment corresponding to the water removal method of the present invention was performed. As the moisture-containing solid, Australian brown coal, which is brown coal, was used. In order to reproduce the extremely high water content of 60% or more of moisture, the royal charcoal immersed in pure water was depressurized with an aspirator, and the air in the pores was replaced with water. A sample coal was prepared. The wet weight of the sample coal was 5.9 g (1.8 g dry weight, 4.1 g water weight). After that, 55.0 g (purity: 99% or more) of moistened royal charcoal and liquefied dimethyl ether (hereinafter abbreviated as DME) are sealed in a transparent container cooled to _75 ° C in advance, and the container is placed in a thermostatic water bath. Submerged and allowed to stand for 1 hour at a constant temperature of 30 ° C to bring the royal coal into contact with liquefied DME. Thereafter, when DME in the vessel was vaporized under atmospheric pressure, 1.2 g of water was separated from the royal coal at the bottom of the vessel. Figure 4 shows the results. The separated water content was 29 wt% of the water content of the royal coal before treatment. Thus, it was confirmed that water could be easily removed using liquefied DME under temperature conditions close to the outside air temperature.

(Example 2)

Furthermore, dehydration phenomenon, moisture content of dehydrated carbon, dehydration performance, flammability using royal brown coal from Australia (ash content 0.3 wt%, moisture 53.2 wt%, volatile component 27.1 wt%, carbon 19.3 wt%) and liquefied DME Clarification of sedimentation phenomena and rewetting characteristics of dehydrated coal did. Incidentally, in order to dry the royal coal to the same level as bituminous coal, it is necessary to dry at a humidity of about 10%, as is apparent from the adsorption isotherm of water vapor on the royal coal at 25 ° C shown in Fig. 5. Thus, Roy Young coal is extremely difficult to dehydrate. This is because lignite has bulk water condensed on the outer surface and between particles of lignite particles, and capillary condensate and surface adsorbed water inside the lignite pores. Of these, bulk water is the easiest to desorb. Next, capillary condensate has a strong capillary suction force, and therefore has a strong water retention capacity. In addition, surface adsorbed water is water directly adsorbed on the surface of the brown coal pore wall, and is most difficult to dehydrate.

1. Experimental method

In order to adjust the water content of the royal coal to a constant level and use it for experiments, the coal was left standing at the top of a container with water on the bottom, and submerged in a constant temperature water bath at a temperature of 25. (: Loyal coal was moistened in an atmosphere of 100% relative humidity for 1 day or more. The moisture of the moistened Roy Young coal was in the range of 52 ± 2%, although it varied slightly from experiment to experiment. The royal coal thus obtained was in a granular state with a particle size of 5 mm or less, and was used as it was in the experiment.

In the dehydration experiment, liquefied DME packed in a stainless steel container was extruded through a column packed with granular Royen's charcoal with a water content adjusted to a constant value of 5 mm or less using compressed nitrogen of 0.7 to 0.9 MPa to flow. The procedure was performed by collecting the liquefied DME in an empty closed container that stores the liquefied DME, which is arranged at the subsequent stage of the column. While passing through the column, the water of the Roy Young coal is dehydrated by dissolving in the liquefied DME.

The experiment was performed at room temperature, and the flow rate of the liquefied DME was 10 ml / min. The purity of the liquefied DME used in the experiment was over 99%. The saturated vapor pressure of liquefied DME at 20 ° C is 0.51 MPa, and the saturated solubility of water in liquefied DME at 20 ° C is 6.7 wt%, which is the minimum amount required for dissolving water lg (hereinafter referred to as theoretical amount). DME is 14.9g.

2. Dehydration phenomenon

A dehydration experiment was conducted in which 194 wt% of liquefied DME was passed through the column to clarify the characteristics of the dehydration phenomenon.

Liquefaction The volume of dehydrated charcoal obtained as a result of passing DME is about 70% of that before dehydration. Was. Heating the dehydrated charcoal at 107 ° C reduced its weight, and when the components of the evaporated gas were measured by gas chromatography, a large amount of DME was detected. From this, it became clear that a large amount of DME was adsorbed on the dehydrated coal. However, since the liquefied DME itself is a fuel, even if it remains in the coal, there is almost no problem when burning the coal.

Here, the liquefied DME discharged from the column is brownish brown and transparent, and it is considered that some of the combustible components of the royal coal have been dissolved. The liquefied DME was evaporated, and impurities contained in the obtained DME gas were measured by gas chromatography. As impurities other than the DME gas, only trace amounts of water vapor and nitrogen were detected. From this, it was confirmed that the evaporated DME contained almost no impurities and was recyclable.

Also, on the trace of evaporation of the liquefied DME from the column, a brownish turbid wastewater and a brown solid (hereinafter referred to as a precipitate), which is considered to be a combustible component of brown coal, were deposited. The precipitate was soluble in ethanol and flammable.

3. Moisture content of dehydrated coal and material balance before and after dehydration

The water removed from the coal in the above-mentioned dehydration experiment, that is, the drainage weight was 4.23 g. Here, the moisture content of the royal coal before dehydration can be measured by the usual moisture measurement method, because DME adsorbed on the dehydrated coal evaporates at 107 ° C, making it impossible to measure only the moisture of the dehydrated coal. It is. Therefore, the calculation was performed using the water content (53.2%) obtained using the same lot of charcoal subjected to the same wet operation. The calculated water content before dehydration of the charcoal was 4.43 g. Therefore, the difference of 0.20 g was defined as the water content of the dehydrated coal. As a result, it was found that the moisture content of the dewatered coal was 4.7% of the total weight of 4.74 g, and that the royal coal could be dewatered as much as bituminous coal.

In addition, the total weight of dehydrated coal, wastewater, and precipitates is 9.43 g, which is l.l lg heavier than the wet weight of the royal coal before dehydration, but this is DME adsorbed on the dehydrated coal. Of these, the weight loss when the dehydrated coal was heated at 107 for 1 hour was 0.59 g, and the remaining 0.52 g had not evaporated, so about half of the adsorbed DME was strongly bound to Roy Young coal. It turned out to be DME.

The weight of the precipitate is 12% by weight of the dry weight of the royal coal before dehydration. Upon heating and evaporation, a brown solid corresponding to a concentration of 1500-2000 ppm precipitated.

4. Dehydration performance

Next, we conducted various experiments on dehydration of royal coal with varying the amount of liquefied DME. Figure 6 shows the results. The amount of wastewater on the vertical axis is standardized based on the water content of the royal coal before dehydration, and the amount of liquefied DME flowing on the horizontal axis is standardized based on the theoretical amount. The dashed line in the figure is the amount of wastewater when lignite moisture is dissolved and dissolved in liquefied DME.

As shown in Fig. 6, when the flow rate of liquefied DME is small and dewatering from the royal coal is not progressing, the brown coal moisture is saturated and dissolved in the liquefied DME, The largest amount of coal moisture was removed. This is considered to be due to the fact that, of the moisture of the royal coal, the bulk water, which is easily desorbed, was dissolved in liquefied DME.

Increasing the flow of liquefied DME increased the amount of wastewater in proportion to the flow until about 80% of the initial water content of the royal coal was removed. When about 80% of the initial water content of Roy Young coal was removed, the amount of liquefied DME required for dehydration increased rapidly. This was because the liquefied DME was discharged from the column without being saturated with water, and required about 6 times the theoretical amount of liquefied DME (dotted line). This is probably because capillary condensed water and adsorbed water remain inside the pores of the royal coal, and the water concentration in the liquefied DME, which is in equilibrium with these waters, is low.

As described above, in the initial stage of dehydration of the royal coal, which contains a large amount of Balta water, a saturable amount of water can be dissolved in the liquefied DME. . On the other hand, if the dewatering of Roy Young coal progresses and only the capillary condensed water and adsorption water remain, it is necessary to use liquefied DME with a low water concentration. From this, it was clarified that if a countercurrent contact type dehydrator was adopted, it would be possible to dehydrate as much as bituminous coal while keeping the liquefied DME flow rate at the theoretical level.

5. Precipitation of combustibles

Fig. 6 also shows the relationship between the amount of liquefied DME and the amount of precipitation (Hatoshi). The weight of the precipitates on the vertical axis is standardized by the dry weight (combustible content weight) of the Roy Young coal before dehydration. As shown in Fig. 6, it is desirable to increase the amount of liquefied DME beyond the theoretical amount in order to improve the dewatering performance, but on the other hand, the weight of the precipitate is proportional to the amount of DME flowing Therefore, it is preferable to dehydrate with a stoichiometric amount of liquefied DME in order to prevent the flammable content of Roy Young coal from decreasing. For this reason, the contact between the royal coal and the liquefied DME by countercurrent contact is preferred.

6. Rewetting characteristics of dehydrated coal

When the dehydrated coal was left in an atmosphere at a temperature of 25 ° C and a relative humidity of 80% for 24 hours, the moisture content of the dehydrated coal after 24 hours increased only to 7.1%. As shown in Fig. 2, if the royal coal before the dehydration treatment was left for 24 hours in an atmosphere at a temperature of 25 ° C and a relative humidity of 78%, it was wetted to 29% water, and the rewet of the dehydrated coal was suppressed. It became clear that there was.

One possible reason for this is that the water molecules must dissolve into the DME molecular population adsorbed on the surface of the dehydrated coal in order for the dehydrated coal to re-wet. As described above, the saturated solubility of water in liquefied DME is about 6.7 wt%, and it is considered that the re-wetting of the dehydrated carbon is suppressed because water at or above the saturated solubility does not dissolve.

As described above, the existing method requires measures such as adding heavy oil to control rewet, whereas the method of the present invention does not require special measures to control rewet. have.

Industrial applications

As described above, the method for removing solid-containing moisture according to the present invention is suitable for removing moisture from a solid containing a large amount of moisture with low power. In particular, the method for removing functional groups on the surface of coal from lignite or sub-bituminous coal. It is useful as a technology that can remove the water in the coal that is strongly bound with low power and dewater it to the water content equivalent to bituminous coal.

Therefore, lignite and sub-bituminous coal, which is low-ash and low-sulfur coal, has low water content and low combustion cost due to its low water content and high flammability. Combustion performance and transportation costs can be realized. This is effective in reducing power generation costs when comprehensively assessing from mining of coal to treatment after power generation. Of course, the present invention can be expected to achieve highly efficient dehydration from a water-containing solid other than coal such as lignite at a room temperature of around 0.5 MPa and operating under extremely easy conditions with low power.

Claims

The scope of the claims

1. Contact a liquefied substance of a substance that is gaseous at 25 ° C and 1 atm (hereinafter referred to as “substance D”) with the water-containing solid to dissolve the solid-containing moisture in the liquefied substance of substance D. By removing solid water by making it a liquefied substance of highly hydrated substance D, vaporizing substance D in the liquefied substance of highly hydrated substance D separates gas and water from substance D, A liquefaction characterized by collecting the separated substance D gas, liquefying the collected gas by pressurizing or cooling, or by using a combination of pressurizing and cooling, and using it again for removing the water content of the water-containing solid. A method for removing solid-containing moisture using a substance.

2. The method according to claim 1, wherein the substance that is gaseous at 25 ° C. and 1 atm is one or a mixture of two or more selected from dimethyl ether, ethyl methyl ether, formaldehyde, ketene, and acetoaldehyde.

3. The method according to claim 1, wherein the water-containing solid is lignite or subbituminous coal.

4. The method according to claim 1, wherein the liquefied substance of the substance D and the water-containing solid are in countercurrent contact with each other.

5. The method according to claim 1, wherein the liquefied substance of the substance D in contact with the water-containing solid is in a stoichiometric amount.

6. The method according to claim 1, wherein the liquefied substance of the substance D is subjected to a series of dehydration operations in a temperature range of 0 ° (: to 50 ° C).

7. Lignite or sub-bituminous coal dehydrated by the method for removing solid-containing moisture according to claim 1.

8. A substance which is a gas at 25 ° C. and 1 atm (hereinafter referred to as a substance D), a compressor for pressurizing the gas of the substance D, and condensing the pressurized gas of the substance D A condenser for converting the substance D into a liquefied substance; a dehydrator for contacting the liquefied substance of the substance D with a water-containing solid to dissolve water to perform dehydration; and vaporizing the substance D from a liquefied substance of the substance D in which the water is dissolved. An evaporator, a separator for separating the vaporized substance D and water, and an expander for expanding the vaporized substance D are connected in series, and the expander is connected to the compressor to form a circuit. The substance D circulates through this circuit, and the condenser and the evaporator are connected to each other by a heat exchanger. A work removal system, wherein the work is collected as a part of the power of the compressor.

9. The separator is connected to a degassing tower for degassing the substance D from the water separated by the separator, and the degassing tower is connected to the circuit to degas the substance. 9. The moisture removal system for moisture-containing solids according to claim 8, wherein D is collected and returned to said circuit.

10. The moisture removal system for a moisture-containing solid according to claim 8, wherein said dehydrator brings a liquefied substance of said substance D and said moisture-containing solid into countercurrent contact.